Due to disease, trauma, or congenital malformation, the ossicles of the middle ear are sometimes damaged. Pexy is a medical term which generally refers to fixation. Myringo is a medical term generally referring to the ear drum. Myringopexy is a condition where the ear drum becomes fixed to the ossicles. More specifically, myringostapediopexy is a condition where the eardrum is fixed to the stapes with the stapes acting like a columella. Retraction of the ear drum occurs when negative pressure builds up in the middle ear from eustachian dysfunction. Specifically, the tube that leads from the ear to the back of the nose no longer passes air into the middle ear. Under such conditions, a retraction pocket can form in the eardrum and eventually the pocket may turn up skin, forming a skin cyst or cholesteatoma. The entire eardrum collapses and drapes over the bones of the middle ear. Further progression of retraction pockets can cause erosion of the middle ear bones or ossicles. While a ventilation tube is the first corrective step for retraction of the eardrum, in more severe cases a prosthesis may be needed to replace damaged bones.
The distance where a prosthesis may be used can be anywhere from 0.5 mm to 1 mm. Existing middle ear prosthesis used for myringopexy indications require major modifications at the time of surgery. This is because the length of the prosthesis is far too long for the distance between the eardrum and the mobile stapes. It is not uncommon that even when a prosthesis is modified, it is still too long to place between the eardrum and stapes. Additionally, existing prostheses are currently made from materials that are heavy or lack support.
One known prosthesis is mushroom-shaped having an enlarged head and a shaft. The current method of modifying such a prosthesis for myringopexy is to cut the shaft of the prosthesis as short as possible. Additionally, notches in the shaft may need to be added to better fit over the stapes. The current material of choice for such a prosthesis is Plasti-Pore which can be easily cut and shaped. Plasti-Pore is porous polyethylene which permits tissue ingrowth into the interconnecting pores of the implant material. Because of the sponge like characteristics of Plasti-Pore, sound conduction is dampened compared to using a more rigid material. A surgeon may also opt to use just the head or platform of a hydroxylapatite prosthesis. In such a case the shaft which is affixed to the hydroxylapatite head must be removed at the time of surgery. Alternatively, the head can be sold independently. Hydroxylapatite is a ceramic based material that closely mimics natural bone. However, weight of the material can be a concern.
The present invention is directed to improvements in a myringopexy type prosthesis.